Vaapi. The ability to add input types to the decoders plugin: GstVideoGLTextureMeta and DMABuf

[Alexander Yanin]

> I guess you could use glsrcbin or gldownload to convert a GLMemory based buffer
> (with a texture inside) into a dmabuf-based buffer and vaapipostproc would
> upload it into a VA surface and then encoding it.

In 1.14 vaapipostproc only has 'video/x-raw(memory:VASurface)' and
'video/x-raw' sink pads, so there is no DMAbuf. Was it added in later
versions of gstreamer?
In case of DMAbuf input, does DMAbuf -> vaapi conversion implies copy operation?
Is there any sense in adding DMAbuf sink pad directly to vaapi encoder
base class?

Alex